9. 贯穿案例：构建标准IO函数库
//mstdio.h
#ifndef __MSTDIO_H__
#define __MSTDIO_H__ #include <unistd.h> #define MEOF -1 //定义文件末尾标志 //文件读写模式
enum mode{READ, WRITE, APPEND}; //MFILE结构体
typedef struct
{
int _fd;
char* _buffer; //缓冲区
char* _nextc; //下一个字符
int _mode; //读写模式
off_t _left; //剩余多少字节（对于读表示缓冲区中未读的
//字节数对于写，表示缓冲区还剩的空闲空间）
}MFILE, *PMFILE; extern MFILE* mfopen(const char* const pathname, const char* const mode);
extern int mfclose(MFILE* fp);
extern void mfflush(MFILE* fp);
extern MFILE* mfdopen(int fd, const char* const mode);
extern int mfgetc(MFILE* fp);
extern int mfputc(int character, MFILE* fp);
extern int mungetc(int character, MFILE* fp);
extern char* mfgets(char* buff, int size, MFILE* fp);
extern int mfputs(char* buff, MFILE* fp);
extern size_t mfread(void* buff, size_t size, size_t counter, MFILE* fp);
extern size_t mfwrite(void* buff, size_t size, size_t counter, MFILE* fp); #endif
//mstdio.c
#include "mstdio.h"
#include <assert.h>
#include <string.h>
#include <fcntl.h>
#include <malloc.h> #define BUFFER_LEN 1024 MFILE* mfopen(const char* const pathname, const char* const mode)
{
int fd; if(!strcmp(mode, "r")){
fd = open(pathname, O_RDONLY);
}else if(!strcmp(mode, "w")){
fd = open(pathname, O_WRONLY | O_CREAT | O_TRUNC, );
}else if(!strcmp(mode, "a")){
fd = open(pathname, O_WRONLY | O_CREAT | O_APPEND, );
}else{
return NULL;
} if (fd < ) return NULL; return mfdopen(fd, mode);
} int mfclose(MFILE* fp)
{
mfflush(fp); //先刷新缓存 int ret = close(fp->_fd); free(fp->_buffer);
free(fp); return ret;
} void mfflush(MFILE* fp)
{
if(fp->_mode = READ){
fp->_nextc = fp->_buffer;
fp->_left = ;
}else{ //WRITE or APPEND
write(fp->_fd, fp->_buffer, (BUFFER_LEN - fp->_left)); fp->_nextc = fp->_buffer;
fp->_left = BUFFER_LEN;
} } MFILE* mfdopen(int fd, const char* const mode)
{
MFILE* fp = (MFILE*)malloc(sizeof(MFILE));
assert( fp != NULL); //断言fp存在 fp->_buffer = (char*)malloc(BUFFER_LEN); //创建缓冲区
assert(fp->_buffer != NULL); fp->_fd = fd;
fp->_nextc = fp->_buffer; //初始化，指向缓冲区开始处 if(!strcmp(mode, "r")){
fp->_mode = READ;
fp->_left = ; //缓冲区剩余0字节未读取，即全部读完。
} if(!strcmp(mode, "w")){
fp->_mode = WRITE;
fp->_left = BUFFER_LEN; //缓冲区剩BUFFER_LEN未写，即空的
} if(!strcmp(mode, "a")){
fp->_mode = APPEND;
fp->_left = BUFFER_LEN;
} return fp;
} int mfgetc(MFILE* fp)
{
assert(fp->_mode == READ); //只允许读操作 //当缓存中的数据己读取完毕，先从文件中读取一批新的数据
//存入缓存中
if (fp->_left == ){
ssize_t size = read(fp->_fd, fp->_buffer, BUFFER_LEN); assert( size >= ); if(size == ) return MEOF; fp->_nextc = fp->_buffer;
fp->_left = size;
} char c = *(fp->_nextc);
fp->_nextc++;
fp->_left--; return c;
} int mfputc(int character, MFILE* fp)
{
assert(fp->_mode == WRITE || fp->_mode == APPEND); //若缓存己满，则先将缓存中的数据写入到文件中
if(fp->_left == ){
if(write(fp->_fd, fp->_buffer, BUFFER_LEN) != BUFFER_LEN){
return ;
} fp->_nextc = fp->_buffer;
fp->_left = BUFFER_LEN;
} *(fp->_nextc) = (char)character;
fp->_nextc++;
fp->_left--; return ; //返回成功写入的字符个数
} int mungetc(int character, MFILE* fp)
{
int ret = ; return ret;
} char* mfgets(char* buff, int size, MFILE* fp)
{
char* ret = NULL; return ret;
} int mfputs(char* buff, MFILE* fp)
{
int ret = ; return ret;
} size_t mfread(void* buff, size_t size, size_t counter, MFILE* fp)
{
size_t ret = ; return ret;
} size_t mfwrite(void* buff, size_t size, size_t counter, MFILE* fp)
{
size_t ret = ; return ret;
}
//mstdio_test.c
#include "mstdio.h"
#include <stdio.h>
#include <stdlib.h>
#include <assert.h> int main(int argc, char* argv[])
{ MFILE* fp1 = mfopen("/etc/passwd", "r");
assert(fp1 != NULL); MFILE* fp2 = mfopen("mypasswd", "w");
assert( fp2 != NULL); char c;
while((c=mfgetc(fp1)) != MEOF){
mfputc(c, fp2);
} mfclose(fp1);
mfclose(fp2); return ;
}